Ms Powell, who has visited Brady regularly since 1999, said she saw signs of dementia and believed he was nearing the end of his life, during a recent meeting.

But she insisted Brady denied there was anything wrong and refused to undergo tests for Alzheimer's.

Brady and Myra Hindley were jailed in 1966 for life for the Moors murders [PA]

She said: "Brady has to be in control and getting dementia is his worst nightmare.

"No one who meets him could ever deny that he had a very sharp mind. He is highly intelligent and insists on dealing with things on his own terms. He never wants to expose his feelings so he is terrified of losing his self-control.

"Everything he does has always been very calculated and he could not imagine anything worse than his own mind slipping away from him.

"He'd never admit it, but I believe he is frightened about what is happening to him."

Brady has been held at Ashworth high-security psychiatric hospital in Liverpool since 1985.